The present invention relates to a diagnosis system for internal combustion engines, and more particularly to a system for diagnosing trouble of a mechanical part of a device such as an actuator, pump mounted on a motor vehicle or a relay for actuating the pump.
Trouble of a mechanical part, such as a pump, a movable member or an actuator can not be monitored by an electrical diagnosis system. In conventional trouble diagnosis, trouble of a part is detected by hearing sound emitted from the part during the operation thereof. However, it is difficult to judge trouble of a continuously operating device such as a pump, since the operation sound is at a constant level and noise emitted from other devices is very loud compared with the operation sound. On the other hand, a relay for actuating the pump must be checked at the exciting time of the relay. However, it is difficult to coincide the checking time with the exciting time.